1. Field of the Invention
The present invention relates to a paste composition for an electrode and a photovoltaic cell.
2. Description of the Related Art
Generally, a crystalline silicon photovoltaic cell is provided with a surface electrode, in which the wiring resistance or contact resistance of the surface electrode is related to a voltage loss associated with conversion efficiency, and further, the wiring width or shape has an influence on the amount of the incident sunlight (see, for example, “Sunlight Power Generation, Newest Technology and Systems”, edited by Yoshihiro Hamakawa, CMC Books, 2001, p. 26-27).
The surface electrode of a photovoltaic cell is usually formed in the following manner. That is, a conductive composition is applied onto an n-type semiconductor layer, which is formed by thermally diffusing phosphorous and the like at a high temperature on the light-receiving surface side of a p-type silicon substrate, by screen printing or the like, and sintered at a high temperature of 800 to 900° C., thereby forming a surface electrode. This conductive composition for forming the surface electrode includes conductive metal powders, glass particles, various additives, and the like.
As the conductive metal powders, silver powders are generally used, but the use of metal powders other than silver powders has been investigated for various reasons. For example, a conductive composition capable of forming an electrode for a photovoltaic cell, including silver and aluminum, is disclosed (see, for example, Japanese Patent Application Laid-Open (JP-A) No. 2006-313744). In addition, a composition for forming an electrode, including metal nanoparticles including silver and metal particles other than silver, is disclosed (see, for example, JP-A No. 2008-226816).